The Roman Catholic bishops of the Flanders (Flemish-speaking) province of Belgium issued a document in September 2022 that allows priests to bless same-sex unions – despite the Vatican’s prohibition of such blessings. They said their decision is not intended as an act of resistance against the Vatican but as a positive move showing that the Church is a welcoming place that does not exclude anyone. For more details see https://www.euronews.com/2022/09/20/belgian-bishops-agree-to-bless-same-sex-unions-defying-vatican.
As in many other continental European countries, the only form of marriage legally recognized in Belgium is civil marriage, so it is not possible for the Church to marry couples.