Hi dathai
Ah yes...wee Joseph

Benedetta is 50, husband been gone well over a year…..
The manifest does list the children travelling with her in order of age - but it doesn't indicate the children's relationship to her (or to the husband to whom she is going).
There are two manifests - one prepared by the departing port, the other for the arrival.
On the former (Benedetta is listed Mrs B ANTONELLI), Joseph is listed as
3/
12 (3 months old.
On the latter, he's definitely listed as 3 weeks old.
My first instinct is to look at the 19 year old daughter as the mother....
SP has one birth registered of only one Joseph ANTONELLI in 1912, and it's in St Giles, Midlothian
(and there are no births that year in all Midlothian where there is a forename containing *epp* (for Giuseppi)).
Cheers
AMBLY