The couple, who have never lived together but had a short relationship in 2013, have been unable to resolve the issue for two years and are now heading to court for the second time to find a solution.
Ms Reynolds wants her surname used, but Mr Sherman wants their son to have a double-barrelled surname.
Although both parents have happily agreed shared parenting, the surname still remains as issue so the boy's name has never been formally registered.
Last year, the couple attended a court hearing to discuss the difficulties of having a double-barrelled surname which included "trouble fitting a hyphenated surname on the top of homework sheets or on lunch boxes" according to The Guardian.
Other difficulties raised included the issue of marrying someone who also had a double-barrelled surname, which we're pretty sure could be resolved if that ever did happen.
The father understandably didn't want his son to "disengage" with him if he didn't have his surname at all.
During the trial last year, the judge said according to The Guardian: "The child has two parents and I consider it is in his best interests to have a hyphenated surname."
She instructed the parents to use the surname [Sherman-Reynolds] at all times, however, the decision was appealed and the case was won.
The judge said on accepting the rehearing: "We consider that a dispute about the name by which a child will be known perhaps for his entire life is a matter of real importance."