Want to add a 3rd cat but not sure if it will be the right choice

I have 2 cats already, they have just turned 1 years old and are brother and sister but my male is more active and playful than my female. They don't really play together, they chase one another and he sometimes gets too much for her. He jumps on her and she'll run away and hide from him then he gives her space and later will try to groom her but she doesn't really want anything to do with him. They use to sleep together but that stoped when the reached 5 months of age. So I would like to know if I adopted another cat, most likely a male that can match his activity level would they play together or would they gang upon my female and make her life hell. My male seems to be a beta personality, active, vocal and very playful where my female is more of a gamma, laid back, she likes people but shes not really a lap cat and she isnt that playful.

I was in your same situation.  I have two cats a boy and a girl too and they  also just made a year. My boy Benjamin would play so rough with my little Caya.  She just wants to relax but he would not allow it.  They do have their loving moments though. It is a typical sister/brother relationship.  I wasn't really planning on adopting another cat but I saw a cat that has been up for adoption for her whole life.  Her name is Nina and she was burned as a kitten and had to have her ear removed.  She just made a year old too. She was in a foster home and was used to being in a multi cat house.  Her foster mom said that she was very social and she liked being around other cats.  She doesn't want to be the boss. She is a great addition to our family.    It was definitely the right choice for us.  At first I wasn't sure how it would work out because it was a little tense but they all get along very well now.  Nina and Benjamin play and run all day and it gives my little Caya time to get her beauty sleep. I hope that it works out for you like it did for me. 

Its made me happy reading about your situation with 3 cats and I never would have thought that a male and female would be able to play nice together but reading that yours does has given me more options to think about. Is there a big difference between having 3 cats as having 2? I know i would need more litter boxes and food dishes but other than that is it a big step?

I really didn't notice any difference going from 2 to 3.  They do each have their own litter boxes and food bowls but they always end up using the one that is not technically theirs.  A year ago we didn't have any cats.  My husband and I always sit and talk about how boring our lives must have been. But I did have to promise after adopting Nina that I would stay off the SPCA website

Thank you for your help. I feel content with 2 cats but feel like a 3rd could bring benefits to the dynamic if it helped my boy out, he really wants someone to play with and snuggle up to and thats just not in his sisters personality and he likes playing with me but sometimes it isnt enough for him. I wouldnt adopt any more cats I think 3 would be enough. My husband already feels like 2 is enough and says the relationship between brother and sister will just get better with time but I disagree. I'm just looking at options and hoping people share their experiences good or bad. My worst nightmare would be deciding to get a 3rd cat and that change the relationship between them in a bad way or all 3 start fighting but I doubt that would happen. It breaks my heart seeing all the cats/kittens that need homes but I want to do the right thing for the cats that I have.