The pair revealed the news via an Instagram post and a newspaper interview, Brunt having made the proposal to Sciver on New Year's Eve last year. They had informed their team-mates immediately, but had not gone public with their relationship till now.
Brunt told The Guardian that she had found telling her parents about their relationship "really difficult", but that she had "seen sense" as she got older.
"My parents are different to Natalie's," she said. "They are quite Christian so it is not something that is done and that's why it has held me back. They don't believe in the way I choose to live my life, basically, so it has been quite difficult.
"Having to tell my parents was really difficult because I care a lot about them so it was something I put off for a long, long time. But as I have got older, I have seen sense and realised that it is not about that, it is about being yourself and living life properly.
"My parents love me: there is no questioning that. They will always be there for me and support me. They are still my parents and they still love me, so it is a compromise I have to take but I am ok with that."
The two first played for England together in 2013, and have both been regulars in the side ever since. Brunt first asked Sciver to be her girlfriend in the hours immediately after the World Cup final win against India in 2017 on the Lord's balcony, and proposed 18 months later.
The pair has also played together at Perth Scorchers in the WBBL, and were both announced as signings for the Trent Rockets at last week's launch of The Hundred.
They plan to get married after England's series against India next September.
Sciver and Brunt join a number of high-profile couples in the women's game, including South Africans Dane van Niekerk and Marizanne Kapp, and New Zealand pair Amy Satterthwaite and Lea Tahuhu.