Rochelle, 24, who has previously said she's like an older sister to the One Direction singer, is holding the bottle for Niall, while Marvin playfully strokes his hair.
"@MarvinHumes and I doing the night feed ;) @niallofficial," wrote Rochelle. Niall then retweeted: "Thanks mammy and daddy."
The next morning the boy band singer wrote to thank the couple for the evening, revealing that he finally got to meet their baby daughter, who was born in May. "Really good laugh last night with @RochelleTheSats and @MarvinHumes, finally got around before Alaia-Mai's bedtime and met the little cutie."
The 19-year-old pop star still had energy for a laugh despite having just wrapped up One Direction’s world tour and attending the Teen Choice Awards in Los Angeles on Sunday, arriving home the following day.
His North London flat - Marvin's former bachelor pad – is situated just around the corner from the Humes' family home, where they live with their three-month-old daughter Alaia-Mai, making it easy for him to pop in on for a spot of family Humes' time.
Rochelle opened up in an interview last year about their close friendship with Niall and the rest of the One Direction boys: "Niall lives close to us so we make him dinner.
"He talks to us about girls and stuff and I give my input and say, 'You can't go out with her!'
"Any of Niall's girls has to be Rochelle-approved. I'm sure he's a little sod and not innocent, but I like to think he is.
"When 1D first started, they were younger than Marv and looked up to him. They weren't from London so Marv showed them the ropes. They come over to ours a lot."