It is God Who Places Love in People's Hearts

Hold fast to the rope of God all together, and do not separate. Remember God's blessing to you when you were enemies and He joined your hearts together so that you became brothers by His blessing. You were on the very brink of the pit of Fire and He rescued you from it. In this way God makes His Signs clear to you, so that hopefully you will be guided. (Surah Ali 'Imran: 103)

... We gave him judgement while still a child, and tenderness and purity from Us - he had fear of God. (Surah Maryam: 12-13)

As for those who believe and do righteous acts, The All Merciful will bestow His love on them. (Surah Maryam: 96)

Among His Signs is that He created spouses for you of your own kind so that you might find tranquillity in them. And He has placed affection and compassion between you. There are certainly Signs in that for people who reflect. (Surat ar-Rum: 21)

It may well be that God will restore the love between you and those of them who are now your enemies. God is All-Powerful. God is Ever-Forgiving, Most Merciful. (Surat al-Mumtahana: 7)