This is why you can't just assume with manga with a title like "I Want Your Mother to be With Me!" there's a number of assumptions you make. That the title refers to the male-protagonist to one of his peers. That the mother is married but husband is not in the picture. That the feelings toward the mother are romantic on in any other way non-platonic.

Actual Synopsis:

Ryo Ishizuka struggles to hold down a part-time job while also studying for the accountant’s exam. He finds emotional comfort in one of his coworkers, Yuzuki Tachibana, a widow with a young child.
As his attraction toward her grows, he prepares himself to confess his feelings, but what will her reply be? Is love enough to conquer all?
Get ready to be pampered to your heart’s delight by this super-pure rom com, centered around a single mom and a freelancer!