Time with each doesn't need to be a long time, just time without distractions. I find that even spending time in the change rooms with one of the boys on his own after his swimming lesson is appreciated. Or taking one child to a medical appointment without the other. At home it could be reading to one of them while the other sleeps, or having them take turns helping in the kitchen.

Don't beat yourself up. It is hard to find the time and I'm sure you are doing a great job. As they get older and start having more activities it does get a bit easier I think.