How to make a page where two content types are combined
In views you can "Group By" the parent nodes. So if you were using entity references to do the relationship, you would have it as a field in views and group by it.

Are they different content types? How are you relating the children to the parent?

If the default Group By isn't enough, there's a module called Views Field View which can put a view inside a view but that could be a bit unnecessary.