Introducing two kittens of different ages?

I just got a new kitten, Mogget, a few days ago. He's probably 7 weeks old. My other kitten, Seven, is about 5 months old. 

Mogget's been quarantined for the first three days. I've read the cat introduction thread on here, but I also know the first few months are very formative and I don't want him to be locked up for so long, especially since that means he won't have as much human company. Is it better to follow the guide and leave him locked up til 9 weeks, or to rush it and let them both out so long as they're supervised?

Has he been tested yet? Any chance of sickness? I know it may not be the right way but with kitten introductions for me it's easier to say here they are. They are usually more open to another kitten. My Sweet Pea hissed and spit a day or two but her curiosity got the best of her and she wanted to play. I stay at home so it is easier for me to supervise. At night I kept Sassy in the laundry room with a box, food and water. I did it because I couldn't be sure that Sweet Pea wouldn't attack. Plus it lets me know for sure they are boxed trained. 

It's been two weeks and they nap together and Sweet Pea grooms her. Sweet pea is 5 months today and Sassy is about six weeks old. The lady I got her from found her outside and didn't know how to determine her age. 

@Louann Jude  Excellent point about sickness. I've considered that especially since Mogget had symptoms of a URI for the first two days- he was sneezing and one of his eyes was just starting to show signs of conjunctivitis.  I tried hard to quarantine everything the kitten touched- including washing my hands every time I touched the kitten- but my boyfriend wasn't as careful and tossed the blankets Mog was sleeping on onto my bed. And these are the blankets he'd had diarrhea on!

Yay I'm so happy they're already buds! I quarantined just a few days with mine. The vet said you are actually quarantining for the resident cat and not the kitten. So if your resident cat has been vaccinated you should be good.

They look pretty comfortable together.  Best of luck with your little family.  

awww they are too cute 

I also just got a new 11 week kitten 2 days ago. Older one is 5 months. I didn't separate them at all except for at night where the older cat stays with us in the bedroom. Our apartment is a little small and I would feel really bad locking him in the bathroom alone.

Older kitty has been a bit hissy and acting mopey. Not sure if I should just let him ride it out or if I should start over and keep them completely separate for a while? I read that cats have excellent memories tho and if they remember a negative meeting they likely will not accept the newcomer.

Please be sure to get your kittens tested for FIV and Felv before introducing them!  I don't know how infectious FIV is but my cat  has Felv and from what I have read it is