Is this something to see a family counselor/therapist about? Little brother wants me as his mom now?

Therapy is absolutely needed for you and your sibling!!! Therapy is especially needed for your mother, but she probably will just get angry and not want to do it! Your sibling is not establishing attachment with his mother! And is now looking for another mother figure, you guys both need to enter therapy! Its nothing to be ashamed of and therapy is called therapy because its therapeutic!