Scarlett Johansson and Colin Jost are living together and planning to wed

A source told Us Weekly: "Scarlett loves Colin too, and they are in it for the long haul. They have talked about marriage and are fully committed to each other. He is beyond doting to her and loves showing her off when they're out."

And Colin is also close to Scarlett's daughter Rose, four, whose father is Scarlett’s former husband Romain Dauriac.

The insider said: "Colin is also close to Scarlett's daughter, and they have a lot of date nights in together as a family."

However, despite their marriage plans, Scarlett - who was also married to fellow Hollywood star Ryan Reynolds from 2008 until 2011 - previously admitted she doesn't consider monogamy to be natural.

During an interview in 2017, she explained: "I think the idea of marriage is very romantic; it's a beautiful idea, and the practice of it can be a very beautiful thing."

But, she added: "I don't think it's natural to be a monogamous person."

Prior to that, Scarlett discussed her views on monogamy while promoting 'Match Point', the Woody Allen-directed crime thriller that was released in 2005.

Scarlett admitted that while she doesn't regard monogamy as natural, she was still determined to be married to the father of her children.

She shared: "I don't think human beings are monogamous creatures by nature. When I decide I want to have children with somebody, I think it would be nice to be married to that person."