It’s a good idea to keep situations fairly simple. The players will complicate things all on their own. Role-playing games are a lot like stories with four or five or more main characters. However, if you wish to add complications to the adventure, you might find it fruitful to give the uncle some nefarious connections, or to make the uncle innocent but not his cousin. Perhaps his cousin’s money ran out, and he opened his home to unscrupulous individuals; perhaps as a safe house for pirates. Or some item he acquired in the past is desired by underworld figures or night cults. Who knows where he hid it, or what it even looks like? Is it in one of the boxes of his wife’s stuff in the upstairs closet? Is it in plain sight but not obvious?
Maybe it’s even hidden underground, stolen by the Oruat before the passage closed.
Another potential plot thickener is a more classic confused parentage: the character the uncle asks to clean the house is the son of the dead man. When the old man’s wife died in childbirth, the old man gave up on living and was no longer fit to raise a child. The child was sent to a cousin to raise. If this backstory is used, the player needs to know it (and it’s their choice whether it’s true), but of course the character may or may not know.