Can the companion of a person with the 2nd group of disabilities not be a relative...

Yes, it can.

According to clause 2(1) of the Resolution of the CMU "On Approval of the Rules for Crossing the State Border by Citizens of Ukraine", in the event of a state of emergency or martial law being introduced on the territory of Ukraine, persons who provide permanent care for persons with disabilities of group I or II and accompany them have the right to cross the state border such persons to travel outside of Ukraine, in the presence of documents (certificates, certificates) on receipt of compensation (benefits, allowances) for care or documents confirming disability, and an act establishing the fact of providing care. The act of establishing the fact of providing care for a person with a disability of group I or II is drawn up on the basis of an application by a person with a disability of group I or II or a person providing care to the district, district in mm. Kyiv and Sevastopol state administration, the executive body of the village, settlement, city council with a statement about the person providing such care. If a person with a disability of group I or II is a registered internally displaced person, an application for care is submitted at the place of registration of the actual place of residence of such an internally displaced person. On the basis of such an application of a person with a disability of the I or II group or a person who provides care, district, district in mm. In Kyiv and Sevastopol, the state administration, the executive body of the village, settlement, city council, no later than within five working days after the application is received, draws up an act establishing the fact of providing care in an arbitrary form. The specified document is sent to the applicant or issued personally at his request.