Some male dogs just do not get along with other males. It's not unusual that this happens - but it is unusual that they lived together peacefully for three years.
Is there a need for them to spend time together? If not, I wouldn't push the issue. If the male you have now is happily living with other females, then that may be all he is capable of.
Do you live close together? If you visit often; I would take one of the females over to your daughters house to play with her male OR I would put your male in another room when your daughter comes to visit ~ if that is feasible.
My Westie, Ringo, ONLY gets along with females. He is very territorial when other males come around ~ and that's how we ended up with a female yorkie.
Best of luck and maybe a professional trainer can help ~ but, if not, sounds like everyone is doing well except for the visits and you can work around that.
__________________  Mommy to Lucy, Ringo, and Matthew |