My father married a woman with 2 children years ago. He bought a house after he had married her. She died 5 years ago. My father has now passed away and he left no will. Are his stepchildren entitled to anything? We live in Louisiana.

Are we talking legal or moral ?

Legal: it follows the bloodline. From her it passed to him. From him it passes to you.

Now they may have had a claim when she passed as they are her bloodline. It still may not be to late to file for it against the estate.

Moral: If your dad helped raise them for any significant period ( lets just say for more then 3 or 4 years ) then they are your brothers and/or sisters. Be kind and be fair because they too lost someone close to them also.
Also are either of the children minors ?
That would change everything.