United Kingdom, June 9 -- Sienna Miller is engaged.

The Factory Girl actress and partner Oli Green welcomed their second child into the world earlier this year, and now it has been revealed they are taking another step in their relationship and getting married.

The 44-year-old star - who also has daughter Marlowe, 13, with former partner Tom Sturridge, and a two-year-old daughter with Oli - stepped out in Spain last week sporting a huge diamond ring on her engagement finger, walking with her hands in front of her so her jewellery could be seen, and E! News have confirmed the piece is an engagement ring.

The couple are largely private about their lives together, keeping their kids out of the public eye, and it only emerged Sienna had gi...