Bear in mind...this is all speculation. Scripture does not support this idea, however, it does not debunk it either, which makes it fun to think about.
So how awesome would it be if Samson was actually the father of Goliath?
Samson was a man that was chosen of by the LORD before he was born (Judges 13:2-5). The LORD made a promise concerning Samson by telling his parents that he would begin to deliver Israel from the hands of the Philistines (Judges 13:5). The LORD blessed him and the Spirit of God began to stir him (Judges 13:24-25).
He had an attraction towards Philistine women (Judges 14:1-4). He also, by eating honey from the inside of a dead lion's carcass, didn't show really any regard for the Jewish clean and unclean Laws that God had established for His people (Judges 14:5-9).
He went to Gaza and found a harlot and he lay with her (Judges 16:1). He then set his sights upon a Philistine woman named Delilah (Judges 16:4).
After being persuaded by money, Delilah, on a daily basis began insisting that Samson tell her how he may be bound. I am not sure what he was thinking, but after continual annoyance, he told her everything.
His hair was cut, his strength was gone, and the Spirit of God had departed from him. Once bound, he could no longer break free. The Philistines finally had him chained and they forced him into different forms of slavery.
His eyes had been gauged out and one day as he was to entertain the people, he rested himself against two pillars. He prayed to the LORD and the Spirit of God came upon him one last time in order that he may die with the Philistines. He killed more people on this day than he did in his entire life (Judges 16:30).
According to Old Testament history and dating these events appropriately given the timing for other major events in Scripture, Samson was born in 1110 B.C. and he died in 1070 B.C.
We know that Goliath was a Philistine. Other than that, we are not given any information apart from the fact that he was from Gath. He was incredibly strong, bigger than the rest, and referred to as "the Champion of the Philistines" (1 Samuel 17).
David was around seventeen years of age when he defeated Goliath. Goliath's death happened in 1024 B.C. This is only forty-six years after the death of Samson.
We are never told if Samson ever journeyed to Gath (less than thirty miles from Gaza), however, since he had a high attraction for Philistine women and most likely played the harlot with many that are not mentioned in Scripture, what if Samson found a harlot just a few years before his death and she became pregnant with a mighty man who takes after his father?
If we had a fuller perspective into Samson's life, I am confident that we would find more and more of his lack-of-morale type lifestyle. Especially in these idolatrous nations, prostitutes were easy to find and if there is one area in Samson's life that he is weak in it is his sexual desires.
Wouldn't it be insane if God used the sin of Samson to raise up a giant in order that eventually He may raise up David, the humble king of Israel!?
Again, this is speculation, however, if this is true, then it would make perfect since to say during the battle of David and Goliath, David was about seventeen and Goliath was around age forty-seven or so.
God said that Samson would begin to deliver Israel from the Philistines (Judges 13:5). Imagine if God's plan was to raise up a giant among their race in order to crush him by using David. Thus David would finish the delivering of Israel from the Philistines.
If Joshua can lead the Israelite army into full-fledged battle against the Canaanites when he is almost a hundred years old, then I see no problem with saying that Goliath was a champion and went into war with David at about age forty-seven.