I hear people saying both. What's the difference between these two? And yeah, once I heard aunt too as well. It confused me alot. Could someone please state the meaning of these? Ive heard people saying multiple things . As in the biological mother saying im mother to the cute little guy.
There is hardly any difference.
Normally we would just say "She is John's mother.", but we could say "mother to John" or "mother of John".
The simile is perhaps more common "She is like a mother to John" (perhaps she is an older sister who takes care of baby John). The "mother of" form is also seen in "Mary, mother of Jesus", for example. Also, you are unlikely to use "to" in phrases like "mother of three".
The following is based on my own experience with this idiom, not from any in-depth study.
Where a child is specifically named, it is more common to hear, "Mary is John's mother", than it is to hear, "Mary is the mother of John", or "Mary is the mother to John."
'Mother of' or 'mother to' is more commonly heard when referring to the number of children that someone has. e.g. "She is the mother of three children." This usage is somewhat old-fashioned or formal; it is more common to hear, "She has three children."
'Mother of' is more commonly heard than 'mother to'. There is generally no difference in meaning between the two. There are two common exceptions to this.
The first exception is the case when someone raises a child, or children, but did not give birth to them. In that case, especially if they raise the children with great care, love and attention, it is common to hear someone say, "She is 'a mother to' those children", or more commonly, "She is 'like a mother to' those children". In this particular case the article before 'mother' is usually 'a' rather than 'the'. However, even in this case, it is not unusual to hear someone say,"She is the mother of two children by adoption", or "She is the mother of two children by marriage."
The second exception is the case where a person takes very good care of others, especially if he or she frequently offers advice . Such a person is frequently referred to as 'mothering' the people he or she looks after, or being a 'second mother' to them. e.g.:
The second grade teacher was like a mother to her pupils.
The coach was like a mother to the younger members of the team.
Mary was like a mother to the other girls in the sorority.