Josh Brolin's stepmother Barbra Streisand is an ''annoying'' grandmother - but in a ''really great way''.

The 50-year-old actor and his wife Kathryn Boyd are expecting their first child together, and Josh - who already has 30-year-old son Trevor and 28-year-old daughter Eden - has revealed no-one is more excited than his stepmother Barbra, who he jokes has become ''annoying'' with her constant emails asking about the unborn tot.

He said: ''My wife got her a bracelet that said 'Grandma' on it and she started crying. She is one of those ... it's annoying but in a really great way, [with] emails every day and like, 'Hey, I thought of this name, what do you think of that? ... When can I come over and feel the baby?'''

Musical icon Barbra - who has been married to Josh's father James Brolin since 1998 - has even downloaded apps which keep her up to date with her grandchild's growth, and the 'Deadpool 2' star thinks it's ''awesome'' that she's so ''into it''.

Speaking on SiriusXM's 'EW Radio Spotlight', he said: ''You realise she follows all the apps, so you know the baby is as big as a banana, which is always weird to me. I don't want to think of my baby as a banana or any kind of fruit or vegetable.

''She is really into it and I love that she is into it. I mean, it's like very typical Jewish grandmother who is saturated by this event. It's awesome.''

Josh and Kathryn announced their impending arrival last month when Josh took to Instagram to reveal his 30-year-old wife is expecting her first child, and the little one is currently ''no bigger than a sweet potato''.

He wrote: ''There's a new sheriff in town, and she's no bigger than a sweet potato. Hang on to your hats. #jbkbstucktogether #lilbeanterritory #loveisaslovedoes (sic)''