How do you know if your boyfriend is still in love with his kids mom?

There will always be a connection with them through the child so all you can do is ask him and if he says no, then you trust him and carry on with your lives together. unless that is, he is going behind your back and sneaking around, meeting her without your knowledge etc, then you trust your gut. Your gut feeling is different from fear, make sure you listen to the right 'voice'.