Relationship Advice

Long story short…..lost my partner to cancer 3 years ago. Was a long tough battle for both of us.
Met a guy who is so lovely. He moved in, discovered all is not as it seems. His son lives with us full time while my 2 boys are week on week off with their dad. He also has a 5 year old (different mother) who is with us alternate weekends (same weekends I have my kids) and every Wednesday night. This child is simply put a spoilt brat. Complains about every meal and watches tv the whole time he is there.
Never asked real situation why his older son was with him fulltime but his son recently told my son he is kept from his mum and his dad made up stories to police about step dad to keep the son with him and she took out a dvo and he had
To attend anger management classes.
He also has another son (same mother) that lives with the mother fulltime and he hasn’t seen him for 3 years. He has made no attempt to contact his son. Now he has a huge child support bill and he is unbearable to live with.
Partner has made the kids mum out to be the bad one but I now think he is some if not most of the blame.
This may sound bad but I like my drama free happy live. Losing a partner and seeing him fade away before my eyes has given me a different outlook on life/ I get alone well with my kids dad and neither of us pay child support and we have no arguements etc I just struggle to deal with his negativity in front of his child toward his ex.
I don’t know where to go from here. I do love him but I also love my drama free cruisey life