Olivia Munn and John Mulaney officially have double trouble in their home ... welcoming kid #2 earlier this month via surrogate -- this after she revealed she had breast cancer.
Munn shared the news to Instagram Sunday ... posting several pics of herself and Mulaney with their newborn -- Méi June Mulaney, a girl, born Saturday, September 14.
OM explains the two used a surrogate ... adding she had very strong feelings about not carrying her own baby this time around -- but, their surrogate showed her grace and helped her put her mind at ease.
Munn ends her post by sharing her daughter's cute nickname -- "Plum" -- 'cause that's what Méi means in Chinese.
John and Olivia welcomed their first kiddo -- Malcolm -- back in 2021 ... months after Mulaney divorced his wife and finished a stint in rehab for cocaine addiction.
They have lived happily together since ... though back in March, Olivia revealed she's suffering from breast cancer -- which she was first diagnosed with in 2023.
She's already undergone a double mastectomy and several other surgeries -- including a hysterectomy, hence needing a surrogate to carry the child.
Olivia and John officially tied the knot back in July, legally cementing their family ... and, it looks like they're adding to it here. Congrats you two!