@Azsy
No, Petrov's family is suppose to support and provide men to the Duke's coalition of forces.
Petrov's family has to provide at least 25 knights (fully armored, trained cavalry) and their squires, the numbers will be a minimum of 50 if each knight only bring 1 squire. Then followed by 40 mercenary infantry, and lastly at least 100 militia (untrained, drafted, most likely spear wielding). This means around 200 men will be provided by Petrov's household.
Though the numbers are not shared yet, but the overall army that will march to Bordertown will be around
.
Also the nobles are unaware that Bordertown has already trained a militia of their own. So they do not consider them as 'soldiers' and only count the number of the Prince's personal guards/knights which number about 50.