My sister and her partner of 3 years separated approx 12 months…

Absent a court order or a previously mediated agreement, neither a solicitor nor the father can order your sister to hand over her sick child (be warned, the reverse is also true and if, for example the father at some time refused to return the child, you may find you need a court order to recover the child, though this would probably not be too difficult to obtain).

The most sensible course, if you cannot simply reach some accommodation by negotiating, is to have a mediation, which is a pre-requisite to legal action in any event where you can negotiate all these issues.

No doubt if such a young child is sick it is not unreasonable to keep the child at home, however, the father likely suspects this is just a ruse to deny him access, particularly if it has happened a few weeks in a row.

If the parties mediate they should agree issues such as how to deal with situations such as when the child is sick and travel arrangements.

Young children are particularly fretful when sick and the court may sympathize with your sister retaining custody when the child is sick, but it may be appropriate that if the child has been sick for several weekends in a row, that a doctor's note be provided, and perhaps the father be offered custody on the next weekend, or additional weekends when the child is recovered.

All things being equal the courts often make both parties responsible for the travel and force them to take turns transporting the child. However, if she doesn't have a vehicle and he does this may weigh in her favour, but on the other hand if she has moved away from the father such a distance, then arguably she should bear responsibility for that decision.

Finally, the fact the ex has a vehicle and your sister does not begs the question as to whether they have settled their property entitlements since splitting up. Your sister may have a claim to some of the ex's assets even though the relationship was quite short, and this is especially so if their is a child involved.

If the mediation fails and it does end up in court, your sister should definitely seek the assistance of a family lawyer as a bad outcome in such a dispute can be very difficult to fix later.

I trust the above assists.