C.S. Lewis had 2 stepsons. One of thier names was Douglas
your 5th cousin
He had two stepsons.
David and Douglas
If you have different fathers, you may be related if you share some other ancestor, such as a mother, a grandparent, great grandparent, etc.
Fathers and Sons
Rowan and Liam
Jill Biden has one biological daughter and two stepsons. Her daughter is Ashley Biden and her two stepsons, from her husband's Joe Biden's previous marriage, are Hunter and Beau Biden.
Through their fathers, Neji and Hinata's fathers are twin brothers. Making Neji and Hinata cousins.
They would be called stepsons and stepdaughters.