The ESV says: "Everyone who believes that Jesus is the Christ has been born of God, and everyone who loves the Father loves whoever has been born of him." The Greek reads: "Πᾶς ὁ πιστεύων ὅτι Ἰησοῦς ἐστιν ὁ Χριστός, ἐκ τοῦ θεοῦ γεγέννηται, καὶ πᾶς ὁ ἀγαπῶν τὸν γεννήσαντα ἀγαπᾷ τὸν γεγεννημένον ἐξ αὐτοῦ."
So, everyone who loves the Father will love those who are born of Him. Right? While that is true, it is not exactly what this verse says: And everyone who loves τὸν γεννήσαντα loves the one who is born (begotten) of Him. Who or what is τὸν γεννήσαντα?
This participle γεννήσαντα comes from the verb γεννάω (to beget, to give birth), and it just doesn't flow well into modern English translation here. It would read something like this: Everyone who loves he who begat (the begetter) loves the one who is born of Him. Does that sound strange? This is how Tyndale translated it, nearly 500 years ago, and it survived hundreds of years in the KJV as well. Even in Spanish this wording flows quite nicely (al que engendró), but in modern English...not so much. There is just no natural way to convey this for the 21st century American reader. So why "Father" in the modern translations? The "one who begets" a person is the Father, so I suppose this was substituted in order to take away some of the difficulty.
It is true that if we love the Father we will love those who are born of Him. It is true that the Father is the one who begets sinners unto new life. But looking at this verse literally, do we love "he who begat"? If we do, then we will love those who are begotten of Him. That is a different way of referring to God, but I like it. To me it possesses more weight and clarity and I will not view this verse the same from now on.
So as you may suspect, I prefer literal word-for-word renderings in translation. I find that they often shed the best light and are quite understandable. As you may have heard... "Understand Yoda perfectly well you can, even if natural English speak he does not..."