Do you think that there was some kind of connection between the Irish and the Welsh? Obviously the Celtic connection, but was there something else going on? There are differences her but there are also too many similarities; surely something was happening there. Lugh and Llew are both connected to the Sun, or to rebirth, or to harvest. They are basically fertility deities.
That’s an interesting and complex question. I think there are good reasons to believe that the respective mythologies of the Welsh and Irish influenced each other, whether this be because of a common origin or rather because of medieval influences is difficult to say. Given that the during the great age of the Celtic Saints, there were people going back and forth over the Irish Sea and also farther afield to Cornwall and Brittany quite a lot, I do think it’s plausible. Let’s not forget that these Celtic literatures were also part of a far wider group of literatures and the Celtic monasteries were great centres of learning in which the respective literatures of the Greek and Roman world would also have been studied too. As well as this, the Irish settled parts of Wales and Cornwall and there is a theory that Ogham might have actually developed in Britain among the Irish settlers and then been transported “back” over the Irish Sea; there are certainly a lot of Ogham stones in the western parts of Britain and these are the areas that coincide with this Irish settlement. I don’t think there are any in Brittany.
Whether Lugh and Lleu are solar divinities is a moot point. In the past it was a belief that pan-Celtic Lugus was derived from a word that would indicate bright light and thus the sun, now it isn’t so certain and various proposals have been offered including a god of oaths, which is interesting. Furthermore, an interpretation of the Roman interpretation of Celtic deities would appear to associate Lugus with Mercury and not with the sun. For me, the biggest issue is that it seems that Celtic belief-systems may have seen the sun as feminine and the moon as masculine, perhaps we should be looking for a sun goddess and not a god at all. It’s all very confusing and conflicting at the best of times, so there’s little that we can say definitively. Nonetheless, I’d say we should consider the following questions:
1. What does Lugus represent or mean in Celtiberian and Gaulish traditions?
2. Can we be sure that Lugh and Lleu are indeed “descended” from Lugus?
3. Can we be sure that Lugh and Lleu are actually “gods” in the Irish and Welsh literature?
4. To what extent might the medieval literatures influenced each other at more or less the same time?
5. To what extent can we ascribe similarities to a common origin rather than mere coincidence?
Anyway, I know that probably asks more questions that it answers, but I hope it helps.