The 27-year-old actor shared the pregnancy announcement on his Instagram page, revealing that he and his spouse had suffered "multiple miscarriages" in their journey to falling pregnant again.
"Absolutely thrilled to announce that Baby Girl #2 is well on the way!!" he wrote alongside a snap of himself, London and their two-year-old daughter Rosie. "After multiple previous miscarriages, we can thankfully report that mom and baby are doing perfectly so far. Yet another reason to be excited for 2021!!!"
Meanwhile, London shared a snap of herself holding an apple against her growing baby bump, as she wrote in the caption, "Our newest Baby Kress - After multiple miscarriages, you have been so carefully and specifically chosen. It is YOU. NOW. We are over the sun, moon and stars excited to meet you!"
"You were the size of an apple in these photos taken a couple weeks ago, & we are not taking for granted each week that you continue to grow (it's amazing we're almost halfway through the pregnancy!). We know nothing is ever certain, but what is certain is that no matter what, you are being fully celebrated by mommy, daddy & your big sister Rosie!"
Nathan, who played Freddie Benson on the popular kids show between 2007 and 2012, and London wed in 2015. They welcomed their first child in December 2017.
Alluding to her past miscarriages, London also said on her pregnancy announcement, "We know that everything happens for a reason, & you are that reason, my precious one. We cannot wait to meet you, baby girl."