Murgatroyd later shared photos from the "special" moment on social media.
Maksim's brother Val Chmerkovskiy and his wife Jenna Johnson welcomed baby Rome, their first child together, on Jan. 10.
On Tuesday, Murgatroyd shared several photos on Instagram with her husband and their 6-year-old son Shai doting over baby Rome.
"One of the most special nights for our families," Murgatroyd captioned her post. "New life, new purpose and new joy! It’s been so sweet seeing the both of you @jennajohnson @valentin parent this little angel."
"We love you all so much XO" she added.
"Rome loves you so much," Johnson commented on the post that same day.
Johnson shared her own snaps from the sweet family night in a recent "Rome recap" that she shared on her Instagram account.
Murgatroyd also announced last month that she and Maks Chmerkovskiy are expecting their second child in June.