Hi drew,
All you owe your (half? step?) sibling and her mother is politeness.
Your dad cannot say “Have a relationship with these folk if you want one with me”.
Tell him “I always let people have their own relationship with each other. We do have a relationship, Dad. We’re just not that close.”
It is his choice whether to have a relationship with you and to what extent. If he puts artificial limits on it, OH WELL! This nonsense going on in his head is probably why he got divorced twice!
Good Luck,
Inky
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