Alec Baldwin has quipped that his and Hilaria Baldwin's children are ''outpacing'' their ability to house them as they prepare for the arrival of their fourth child in four years.

The 59-year-old actor and his wife - who have Carmen, four, Rafael, two, and 18-month-old Leonardo together - are gearing up for the arrival of their son and Alec has joked he'll be opening up a hotel soon to house his ever growing family.

He shared: ''We're having children - it's outpacing our ability to house them. I said to my wife, 'This one, we're going to have to put him in a hotel. He'll be nearby.' ...

''My daughter Carmen said, 'You have to have another one. We have to have another girl so we have another girl in the house. And my wife says to me, 'I want to have maybe one more, Alec. We have one girl.' And I said, 'I hope you and your next husband are very happy together.'''

And Alec - who also has 22-year-old daughter Ireland with his ex Kim Basinger - is so proud of his wife Hilaria, who he has dubbed the ''greatest mom''.

Speaking on The Tonight Show with Jimmy Fallon, he added: ''It makes me cry. She's the greatest mom.''

Meanwhile, Hilaria previously revealed she ''really likes'' being a mother.

She explained: ''I never knew how many kids I wanted to have. I didn't know how much I'd like it. And I really, really like it ...We were like, 'Oh, should we have another kid?' We were like, 'You know what? Let's try something different - let's try.' [With] the other ones, it's not like we were like, 'Oh my God, how did this happen?' But this is the only one we [planned].''