Possibly The Powers Of Matthew Star.
The answer to this earlier question.
In the show there is this guy and he has abilities...not really like showy powers.
Matthew's powers during this season were mainly telekinetic, being able to move objects with the power of his mind. This power was illustrated in the opening credits as moving a book back into a slot on a bookshelf. In episodes, he used telekinesis to manipulate a football, and raise rocks that had buried an experimental Air Force flying unit and then its simulation.
I think he knows he's from another planet.
It starred Peter Barton as the title character, the alien prince Matthew "E'Hawke" Star of the planet Quadris, who used his powers to fight crime.
He looks up to a star and has a birthmark, I think.
From the previous thread.
I vaguely recall that the young man has a mark on his forehead (possibly star-shaped) that is normally invisible but that can glow. (When he uses his psi powers?) This mark is the sign that he is the true heir to his fathers kingdom.
He does not have a good relationship with his mother.
In the episode "Mother," a strange carnival gypsy is revealed to be Matthew's mother, Nadra, who had been traveling the galaxy and hiding from assassins. This reunion was bittersweet; due to Nadra's health problems, she was forced to leave Crestridge for an undisclosed location at a higher elevation.