Good suggestions! I have no idea why they don't like each other. They will tolerate each other most of time, but if one gets into the "space" of the other one----well, not fun. My husband thinks it's a game between them, maybe he's right. In fact I've caught one of them hiding around the corner laying in wait for the other one to show up. I've also caught one of them sitting on the floor about 12" away, staring at the other one who is sound asleep waiting for him to wake up.
As far as keeping them active, since they're indoor/outdoor cats they're gone most of the times prowling the neighborhood, so most of this happens at night when they've come in for dinner and bedtime.
I won't even mention the RD MALE cat that my neighbor dumped on all of us in the neighborhood after she move away and left him. Guess who's taking care of him also. This one though I can look after in our office which is away from the main house, so not quite so bad.
Gee, all I ever wanted was a sweet, funny lovable cat who'll play with me, and all I've gotten are 3 males who don't particularly like being fussed over by me, and as an added bonus don't even like each other. Lucky, lucky me :-)
that is how it seems to go. I have MANY outdoor cats that are drop offs. varying degrees of friendliness.. but they are strays & would NOT let me touch them,yet alone pick them up & cuddle.
My indoor/outdoor population grows by leaps & bounds. I have many friendly cuddly ones & they are a joy. My cali(see profile page) is now on my lap & struggles to sit on keyboard. Have had her since 1988 & she is a sweet. loving cat.. but I have had many males that are much warmer & cuddly.
your male cats sound like a typical male dominance/territory thing.