I have 3 cats, who are 6 and 7 years old. I also have 3yo DS and 6mo DD.
One of the cats, the older one, is fairly adaptable and well-behaved, bar a fondness for clawing leather. The younger two are littermates who arrived together and have always thought of themselves as a unit. The female is mildly suspicious of changes but fairly independent, the male hates it and dislikes anything out of the usual peaceful life.
The younger two have started showing some worrying behaviours which have worsened when they get stressed. The male wees on things when he is given less attention - we were away for NYE for 3 days and when we came back he had pissed on DD's playmat and toys on the floor. He used to wee on our bed when we were away, so we shut the bedroom doors, then he would do it whenever we returned from holiday, but I make a massive fuss of him as soon as I see him on my return and that makes a difference - when he feels loved he doesn't pee. When I got a new job working full-time in 2014, he started urinating in the bathroom sinks and on bath mats/towels left on the floor. He got a lot better when I went part-time in pregnancy last winter and spent more time lying around cuddling him, but now I'm on mat leave and DS is home from preschool with me and the baby, the behaviour has ramped up again. The female cat has had some stress-aggravated/related skin problems. Both boy and girl have turned aggressive with the older cat and they are now fighting pretty frequently, whereas they spent 6 years peacefully co-existing before this.
I'm spending £45 a month on Feliway and it's not helping much if at all. Bought new and extra litterboxes. They're indoor only, because they are pedigree and as lovingly daft as the teddybears they so resemble. We have been trying to sell our flat and move out to a house with more rooms and space to divide up between them and an enclosed garden to roam, but a move fell through in December and it will be months now before we get to that point again. DS is boisterous and not gentle (he's improving, but not quickly enough) and persists in throwing things at them when they hide in corners to try and get them to come out and play with him.
(I used to have a massive cat hair problem, but when my washer/dryer broke DH finally let me buy a dryer and it has changed my world - I can wear black again!)
It's not fair on them to keep them in this household, even though I HATE the thought of giving up my furbabies. They are suffering and there is not a lot I can do to change their environment.