Who played a key role in the Hutu class becoming the rulling power in Rwanda?

Parti du Mouvement de l'Emancipation du Peuple Hutu

Explanation:

The Party for Hutu Emancipation became the spearhead of the revolution under Grégoire Kayibanda, Rwanda's first president.

Grégoire Kayibanda

Explanation:

Independence and the 1960s

Under the leadership of Grégoire Kayibanda, Rwanda's first president, the Party for Hutu Emancipation (Parti du Mouvement de l'Emancipation du Peuple Hutu) emerged as the spearhead of the revolution.

in june, we will have been married for eighteen months. (i am assuming this is what you want? the sentence, as you have presented it, is grammatically incorrect--   you want it corrected, yes? )