Who were the real members of the knights of the round table?

Probably not, in most cases.

The ancient Celts and Romans did not eat at table and early Welsh did not even have a Word for table. The Welsh had to borrow the English Word bord as bwrd. Bordmostly just means 'board'. as a table is just a board set on trestles.

If there was an historical Arthur, he almost certainly did not have a Round Table.

Of the famous knights of the Round Table in European tales, only Kay and Bedivere (under the forms Kai and Bedwyr) appear in surviving early Welsh tales. Tristan appears in some later tales. Gawain appears as Gwalchmei and these two names may earlier have been applied distinct persons.