Grab your tissues ... this tearjerker's brought to you by Kansas City Royals prospect Brady Singer who surprised his parents with a VERY expensive gift that'll earn him an award for Son of the Year.

Singer posted this video on Christmas Day ... which begins with Singer's mom opening a red envelope. She starts reading Singer's heartfelt letter ... and if it doesn't give you all the feels, nothing else will. Singer's mom reads out loud: "I just wanna say thank you for everything you've done to help me reach my dreams ... Both of you constantly took off of work and spent every dime you made just to put a smile on my face."

Then ... her jaw drops. SINGER WIPED OUT THEIR ENTIRE DEBT!!!

Today is very special to my heart. To give back to the two people who have given up everything to support my brother and I. I can’t thank them enough. Love you Mom and Dad pic.twitter.com/AFHi2Xma0c @Bsinger51

Singer was selected by the Kansas City Royals with the 18th overall pick earlier this summer. He's a right-handed pitcher with huge potential ... which explains why the Royals paid him $4.25 million to sign with them instead of returning to Florida.

Another sign the Royals wanted Singer badly? They paid him well above the slot value of an 18th overall pick. Yeah, he's that good. And, he's a byproduct of his parents' hard work and sacrifices ... which is why Singer wanted to SHOCK them with an incredible gesture.