[ Marriage & Divorce ] Open Question : my wife spends too much time with relatives etc?

I am frustrated at the demands made on my wife its already difficult cause she has a son (stepson to me) who is still on the milk but hes almost 20. Its like a constant fight for her attention with everbody else! eg. brothers sisters stepson kids events work more work than me way last place lol. No seriously though? Before I was content to just row the waves but now im getting pretty sick and tired of it. I mean the stepson still lives at home and its like im competing mano a mano with a 20 yr old for my wifes undivided attention! I mean when you grow up your supposed to drink beer but he still likes the milk( figure of speech). And again the sister( well call her sister x) is always in the show. So basically the time for me the wife and my three kids get very little time together just us. What can I do please and thank you very much. Frustrated in Canada