With respect to marriage, priesthood, and celibacy:
In the Church, both Eastern and Western Rites, the rule is that once a man has received the Sacrament of Holy Orders, he may not then receive the Sacrament of Matrimony, ie, contract a marriage. This is a common thread in the priesthood in the Church, and runs all the way through.
So, if a married man is ordained a Vocational Deacon, he remains a married man, but if he is widowed, he cannot remarry. The same provision would apply to a converted Protestant minister who received Holy Orders, under the provisions approved by the Holy Father that dispenses him from the discipline of celibacy.
It should be noted, too, that Eastern Rite Catholics do indeed have priests who are married, but only single, and therefore celibate, priests are consecrated as Bishops. And the married priests must have received the Sacrament of Matrimony before they received the Sacrament of Holy Orders, since they cannot receive Matrimony after Holy Orders.
Blessings,
Gerry