Technically you can't. I suspect that you are the type of person who believes that you have only one father and that your mother is not allowed to move on, or date someone else other that your biological father. classic.
Anyhow, there are a few things you can do.
You can try to persuade your mom to stop dating him(you have to have a good reason, like he's a druggie or something but GENUINE, no lies, she won't appreciate it). Or cause he's real crap to kids.
Tell him straight off that you don't like him and tell him to get out of your life.
Tell your mom your honest opinion and/or you won't put up with him.
Or you can just accept that your mom is allowed to move on and get a new boyfriend.
Unless your mom is cheating on your dad cuz they are still married (don't take offence PLEASE) or shes seems to be hitting on every guy since he left (still PLEASE don't take offence) and you want her to stop it cause it seems childish.
PLEASE DoN'T take offence
I'd add only that you should ask the corollary: what if your mother does not like your boy/girl-friend? (You don't state your own sex so I'm applying this to both.) There is nothing to gained from making someone else unhappy for your own ends.
Sabotage they're love
Wait until your mother and her boyfriend are in the room together and ask, 'Are you going to be my new dad?' This should put him in a hot and stressful situation, a perfect start to slowly driving him out.
What episode does Brooke get a boyfriend
your stuffed
well i would suggest you should confront your mother on this,and if it does not work out id move out
the dick of your moms boyfriend.
No, Chloe is single
ask your mum nicely to ask her boyfriend to respect your privacy.
not as old as your moms boyfriend!
don't know do u??
ur neice-in-law i think
No..he was just her moms ex-lover !
i hate my moms boy friend my brother, my other brother, even my puppy don't like my moms boyfriend, so kids do hate their moms boy friend