Former The Hills star Holly welcomed son Isaiah Hawk Wilson on Sunday, 3 March, her first child with husband Richie Wilson.
Sure-to-be devoted aunt Heidi has now tweeted: "Congratulations to my sister @hollymontag and @wichierilson on their new baby boy, Isaiah Hawk Wilson! #Blessed Can't wait to meet him!"
Heidi has made no secret of the fact she'd also like to start a family. She's been married to The Hills co-star Spencer Pratt for six years.
The couple have had differening views on children in the past, even signing up for US reality show Marriage Bootcamp to address their conflict: Heidi wants kids now, Spencer says he isn't ready.
When a little one does come along, however, Spencer has revealed he already has the name picked out: Speidi.
Yes. Speidi. As in the couple's nickname!
He joked to Us Weekly: "If we named our child Speidi, it would be incredible. It would be Speidi Pratt, legally. If they really didn't like their name when they grew up and were aware of the situation they [could] pick whatever name they want."
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