Lindsay Lohan kissing Rumer WillisAshton Kutcher is finding that it’s hard being a step-dad sometimes - particularly when your step-daughters are hanging out with Hollywood stars with a reputation for partying hard.

Ashton is reportedly annoyed that step-daughter Rumer Willis, from his wife Demi Moore’s previous marriage to Bruce Willis, is spending her first term at university partying with Lindsay Lohan rather than hitting the books.

A source told Life & Style Weekly that “education is very important to Ashton, and he’s afraid Rumer will think partying is better than studying.”

But the source added Rumer isn’t easily swayed from her new friend: “Rumer can’t stop gushing about how cool Lindsay is. [She] feels honored by Lindsay’s attention.”