Slightly shy cats!

So about a week ago( last Wednesday) i adopted a bonded pair ( brother and sister), i was told that these cats were a bit shy but were sweet and playful once they know you. They recently had an eye infection that was cured and were also neutered/ spayed at around the same time. So last wednesday i picked them from the vet and let them roam the apartment ( 1 bedroom apartment with my room's door closed). I tried to socialize with them the first day but they were pretty scared so i left their food, water and litter box to them. The next day i go to pet the male which he allows me to and instantly purs and also guides to the areas he wants me to pet after around 10 mins of petting i leave and go back to my room. I come back later to try and pet him again but as soon as my hands are 5-15 cm close to him he hisses so i go ahead and not provoke a reaction and just leave him. I then ignore both cats trying not to look at them or anything, but put their food closer and closer to me everyday till its about 1-2 meters away. They would come and eat the food while im 1 meters away while i try and ignore them.

So on tuesday i have an appointment with my vet to get them to check up on their surgery, so i tried to bond with them yesterday by playing with a mouse toy and giving them treats when they come out and follow the mouse but not touch it. I thought that now would be a good time to try and pet them again but as soon as i just try and reach out my hands slowly they run away back to their hiding spot. The problem is i dont know how i can gain their trust to put them in the carrier to take them to the vet without them running and going under my couch.  So im going to spend more time today playing with them when they are awake and try and gain their trust. However if this does not work i was wondering if i should just re-schedule the vet appointment to a time where they trust me enough or just try and force them into the carrier which im sure is not a good idea and will scare them a lot!

It will take time for them to get used to you and trust them. Some cats take longer than others to do so. The key is plenty of treats and patience! I found with one of my kitties who is a bit skittish that if i get down on her level she seems to be less timid of me.

If they are well at the moment, I'd call the  vet and reschedule the checkup for another week to give you more time to bond.

Hey!
 

The male is getting used to his new environment more and plays by himself. The problem is sometimes he lets me pet him and  doesn't get scared of me and then suddenly the next time i see him its like hes scared again and were back to square one, no matter how many treats i give him its like he does not trust me anymore even though nothing happened. The female is very very shy she does not eat any treats and just hides anywhere she just wants to get out of sight. So im wondering if i should control when they should eat, because atm i just put their food and water out for them at all times, i just feel like these last 8 days was like a roller coaster ride 1 moment they are not afraid of me and the next thing you know they are back to square one..... really frustrated never happened to any of my previous cats :/...

Time and patience are your friends, and it seems you have some of both. Right now they are still learning what's up, what your routine is, add on that the trip to the vets. Sometimes they are brave, sometimes they get scared. I believe both cats will grow out. And honestly it depends on their DNA (kindof). I volunteer for a cat sanctuary. There are two adorable kittens, brother-sister, there (permanently--they are FeLK+). One is shy, the other, well you look at him, and he purrs. He'll climb on your back, neck, lap, anywhere to get close to you. The sister is more timid.
Do you know what their background is? That can effect/affect how soon they will start to trust you.
Ritz was my first cat ever, and the first four months of her life were probably traumatic. She and her litter mates and mother cat were dumped by my condo in November 2009, survived a 20 inch snow storm, before my friend trapped the litter and socialized them. I helped a little before adopting Ritz.
I let Ritz dictate 100% what she wanted from me. When she jumped up on the sofa or lap, I always make/made sure she had an easy escape, I never boxed her in. I petted her, and stopped before I thought she'd want to (swishing tail is a dead give away).
How old are they? Kittens should eat as much as they want. My approach would be to give them regular food and sit with them when they eat. Give them special treats later on, perhaps after they play (satisfies their prey drive) and if they let you pet them.

Yes, you are right the male if he lets me pet him purs instantly. Well i adopted them from a shelter and were then fostered into a pet shop. The male got adopted but then was suddenly returned. They stayed in that particular pet shop for about a month or 2, then moved to another pet shop of the same company for a month till i adopted them. As far as i can tell the people taking care of them were very nice and knew what they were doing but i suppose living in a cage for 3 months is not nice :/ !

Ferals can take a very long time.  If they didnt get that human interaction when they were just a few days old, it takes longer.  If they were as old as 5 weeks when they were captured, it can take much longer.  Read some threads in the Rescuing Strays and Feral forum to get good ideas.  You really have to let THEM make the moves, and food is a great bribe;  one took a year before she would allow head petting although body petting was fine.  With the head, she would duck and cover.  So I started leaving my hand hanging down by my side, and next thing I knew she was self-petting against my hand.  Moving it spooked her for months but finally she got it and now sits on the railing of the tub while I'm on the toilet and bumps m with her head to be petted.  In short, be in the dance with them, but LET THEM LEAD.

They aren't feral, i asked the shelter where i adopted them from they are just shy and need time, and as of yesterday they have let me pet them and would purr but only when i put out their food.

If he has lived in four or five different places this year, it's easy to see why he acts that way. You don't know what sort of visual cue/memory sets him off. My Regent starts brooding as soon as we grab our car keys, and if he even sees a carrier in the room he goes hysterical.

My advice is to keep the apartment as consistent as possible. Don't wear strong perfume or come in smelling of alcohol. Sit on the floor to be on their level, and go for baby steps.

I would totally suggest moving the vet appointment as long as they are healthy. We took Regent to the vet too soon, and let me tell you, that was a nightmare which reversed almost all of our progress.

Just an update: Both cats are doing great now and are braver. I just have one problem left, whenever my cats do anything good, i give them treats with my hand and pet them, however sometimes if i just touch them for 2 secs they scratch me without any warning no hissing, no tale waging they just scratch me. Now i know the cats may not always want me to touch them but shouldn't they warn me by hissing, tale signs or ears going backward? I was wondering if this was normal or not. Because im starting to get afraid of trying to pet them.

Also i just want to add the fact that when i approach to pet them i go really slowly so i think thats enough time for me to get a message if they want to be pet or not, instead of lashing out on me out of nowhere. 

My Noodles HAS to smell our hands before we can pet her.  I've had her since she was 10 weeks; she is 9 now.  She has always been like this.  I've just come to accept it as one of her quirks.     She doesn't hiss; she just swats.  Sometimes we get bopped just for walking by her.     At this moment she is in my lap kneading me and purring up a storm!