Sienna Miller Reveals Her Third Baby Is a Boy as She Reflects on Motherhood

Sienna Miller has shared a new detail about her growing family: her third child is a baby boy.

The actress, 44, welcomed the newborn in May 2026 with her fiancé, Oli Green. Until now, Miller had kept the baby’s sex private.

In a recent conversation with British Vogue, she also looked back on the unexpected way her family grew after she turned 40. Miller said she once believed she might not have another child, making her later experiences of motherhood particularly meaningful.

Sienna Miller Confirms the Sex of Her Newborn

Miller’s latest revelation confirms that her newest child is a boy.

The newborn is her second child with Green. The couple previously welcomed a daughter in December 2023.

Miller announced the birth of her third child in May during an interview with E! News. At that point, she did not reveal whether the baby was a boy or girl.

She did, however, share a glimpse into those first days as a mother of three. Miller spoke about being exhausted from sleepless nights while also expressing how strongly she felt about her new baby.

The actress has since offered a few glimpses of her life with the newborn, although she has continued to keep many details private.

Motherhood After 40 Was Not Part of Miller’s Original Plan

Miller’s recent comments also provide insight into how she viewed motherhood earlier in her life.

She explained that she had once reached 40 believing that having another child probably would not happen. At that point, she had already accepted the possibility that she might remain a mother to one child.

That expectation eventually changed.

Miller became a mother again in her early 40s and has now welcomed another baby at 44. She described the experience as an unexpected source of happiness and relief.

Her story has therefore taken a very different path from the one she once imagined.

The Actress Is Now Raising Three Children

Miller’s family includes children from different stages of her life.

She shares her oldest daughter, Marlowe, with actor Tom Sturridge. Marlowe was born in 2012.

Miller later started a family with Green. Their first child together, a daughter, arrived in December 2023.

Now, the couple have welcomed their second child together.

That makes Miller a mother of three, with her children spanning from the teenage years to infancy.

Sienna Miller Says Her 40s Brought a Different Perspective

Miller has previously spoken about how her outlook on motherhood changed as she got older.

In a March interview with Glamour, she discussed having children at different points in her life. She said she found motherhood in her 40s easier in some ways because she felt more settled and less divided between competing ambitions.

That sense of perspective appears to have influenced how she approaches family life today.

Rather than feeling the same pressure she experienced in her younger years, Miller has described herself as more comfortable with who she is.

Her comments offer a personal explanation for why this period of motherhood feels different to her.

Miller and Oli Green Continue to Build Their Family

Miller and Green have been together since 2021. Their relationship has since developed into a family life with two children.

Their daughter was born in late 2023, followed by their baby boy in May 2026.

The couple also became engaged in 2026, according to British Vogue.

While Miller occasionally shares moments from her personal life, she generally keeps her children away from the public spotlight. Her recent posts have offered only limited glimpses of the family.

What Miller’s Latest Comments Reveal About Her Life

The arrival of Miller’s third child represents more than another celebrity baby announcement.

It also highlights how dramatically her expectations about motherhood changed over time.

She once thought having more children after 40 might never happen. Instead, she welcomed two children during that decade of her life.

Now, Miller is adjusting to life as a mother of three while continuing her career in film and television.

Her latest comments suggest that she sees this chapter with a greater sense of confidence and calm than she did earlier in adulthood.

Reporting Sources

The information in this article is based on Miller’s comments reported by British Vogue, as well as her May 2026 birth announcement reported by E! News. Previous comments about motherhood in her 40s were reported by Glamour.