Liam Hemsworth won't be marrying Miley Cyrus anytime soon, insists his brother.

The pair sparked wedding rumours after Miley posted a picture on Twitter showing off a manicured hand and what appeared to be an impressive engagement ring. However, the 19-year-old singer later dismissed reports that The Hunger Games star had proposed and now Liam's brother Chris Hemsworth has also waded into the debate.

He believes they are too young to tie the knot just yet.

"They're like 21 or something I can't see that happening," he told E! Online when asked about the marriage speculation. "You have to ask him about his relationship."

While 22-year-old Liam isn't ready to wed Miley just yet, his older brother Chris is happily settled with his wife Elsa Pataky.

The pair are expecting this first child later this year, but 28-year-old Chris is reluctant to give away too many details.

"It's definitely one of them [boy or girl]It's a secret," The Avengers actor smiled.

Liam and Miley began dating after meeting on the set of The Last Song in 2010.

The pop star was quick to dispel wedding rumours last week, insisting she has been wearing the same ring for months.

"I'm not engaged," she wrote on her Twitter page today. "I've worn the same ring on this finger since November! People just wanna find something to [talk] about! It's a topaz people! (sic)"