Biology rules. It's not in our genes.
Our species does not instinctually form lifetime or even long term exclusive pair bonds. If we did we'd bond with the first person with whom we mated and never look anywhere else, fantasize anyone else, lust after anyone else or question the choice we made in a partner.
Millions of animal species. A relative handful form lifetime exclusive pair bonds. Not ours.
It's fighting five million years of hominid evolution including at least 300,000 years of human evolution to think and behave otherwise.
Need more evidence? If we instinctually formed exclusive lifetime pair bonds there would be no need for the religious taboo--the death penalty--for any sexual activity outside of a lifetime exclusive pair bond and a heterosexual one at that.
Give up the myths--religious, romantic, cultural and social--which bind you to this illusion. Accept this of yourself and of other human beings. It's who and what we are. Broken family? You can choose to love them anyway or always be bitter about it. What's your pleasure? Which is easier?