AceShowbiz -

Ian Somerhalder and his girlfriend Nikki Reed are taking their relationship to the next level. The 36-year-old actor is engaged to the 26-year-old actress after six months of dating. "[Ian and Nikki]'re so happy," a source tells E! News.

The source adds, "They were crazy happy from the start. Their families love each other. It just feels really right." According to the source, Ian told Nikki that he had "been in love with [her] for years" long before they're dating.

A second source tells Us Weekly of Nikki, "She accepted with glee. She is madly in love." Another source claims, "They were friends before, the groundwork had been laid before. They had always been attracted to each other, but always in another relationship. It may seem quick, but they knew it was right. They believe in the same things. They are dedicated to their work and helping others."

Nikki was spotted wearing two diamond rings on her right ring finger when accompanying Ian to a Golden Globes after-party hosted by InStyle and Warner Bros. on Sunday, January 11.

This will be the first marriage for Ian and the second for Nikki. The star of "The Vampire Diaries" previously dated his co-star Nina Dobrev for three years before splitting in May 2013.

Nikki, meanwhile, was previously married to "American Idol" alum Paul McDonald in 2011. The "Twilight" actress filed for divorce from Paul in May 2014 and their divorce was finalized earlier this month.