If by the guy you mean Ken, it's alright for now. You'll have the option to share Anna but you don't have to. You can bang his MILF Samantha so I won't recommend to go back/ ignore his quest.
Just a heads up, if you want additional scenes with Samantha then you'll have to share Samantha with Ken. You'll have solo scenes with her but to progress Ken/Samantha arc, you should share her, but the choice is yours.