I’ve got two boys, from the same litter - they’re 7 years old now. They have FIV so when we rescued them we were advised to keep them as house cats.
For the first 5 years of their lives they lived in peaceful luxury... then our son came along!
First 6 months were fine but when he started moving and crawling they started getting angry, not with him but with each other. At one point they couldn’t be in the same room as each other without fighting... and properly fighting, one nearly ripped the ear off the other 
Cue visits to vets and they are now on Zylkene which has helped a lot... our son is now 2 and they fight maybe once a day but without injuries other than the occasional tiny scratch. And they will happily sleep / relax in the same room when it suits them.
The problem is now that I’m about to pop with our second baby. Cats are very aware that the baby stuff has been slowly coming out (have been doing it slowly but surely) and obviously remember what happened last time and are showing their displeasure by weeing on things!!! this is the first time they’ve been upset enough to wee elsewhere than the litter box.
I love them to bits (well, one of them at least!.. the other has become my DHs cat and doesn’t like me anymore) and have no idea what to do next. We’ve had them checked out at vets and no illness that would mean they should be weeing everywhere.
I’m feeling like I can’t cope with a tantruming toddler, a new born and cat piss all over the house!!
I don’t know if it would be fairer on them to try and get them a nice quiet home somewhere (but is anyone actually gonna take on two FIV cats?) and maybe they should be separated anyway?!
Any tips, tricks or advice welcome