Miley Cyrus' younger brother is reportedly dating Patrick Schwarzenegger's older sister.

According to gossip website TMZ, Braison Cyrus, 20, started seeing Christina Schwarzenegger, 23, in December, just a month after Miley, 22, and Patrick, 21, started dating.

Braison has also fuelled such speculation by posting pictures of him and a brunette beauty, who closely resembles Christina, hanging out together on his Instagram account.

What's more, he added a heart emotion to the caption of both images.

Miley and Patrick - whose parents are Arnold Schwarzenegger and his estranged wife Maria Shriver - have been getting on so well in the early stages of their relationship that they are set to get matching ''X-rated'' tattoos.

A source said earlier this month: ''It's not a one way street, he's into her big time. Her wild side does not turn him off. It's to the point where he's getting wilder, he's expanding that side of him.

''He's actually gone so far as to tell her that he wants them to get matching tattoos, below the belt, if you know what I mean. It's so X-rated and of course she's totally down for it!''

Patrick's fondness for Miley - whose parents are Billy Ray and Tish Cyrus - dates back to 2011 when he admitted he was single and liked the 'Wrecking Ball' hitmaker.

He said: ''My eye, though, is set on Miley.''