Can my ex use her sister as her solicitor?

I'm acting as a Litigant in Person in a Section 8 hearing regarding my son. Now my ex knows I have ditched my solicitor I am getting hints that she is going to ditch her current solicitor and instead try to get her sister to represent her.

My understanding is that there are rules on who can be a McKenzie friend (e.g. can't have a personal involvement in the case, must be familiar with the process). Are there similar rules on who can act as a solicitor?

The sister is a practicing solicitor, but not in the field of family law. She lives with the ex and my son, so clearly is not objective. Also, as she lives with my son, I have named the sister in section 8 of the C100.

I wouldnt think this was ethical or in line with the stringent professional practices expected not to mention codes of conduct of solicitors:dry:

E

I think this would be wrong as the other person is having a distinct advantage over the other.But then again knowing the legal system this will probably be ok:)

I think this would be wrong as the other person is having a distinct advantage over the other.But then again knowing the legal system this will probably be ok:)