Bobby Brown & Bobbi Kristina -- Reunited on Father's Day

Bobby Brown and his daughter Bobbi Kristina took a huge hit from the peace pipe this weekend -- and had an emotional reunion on Father's Day.

Here's what we know ... BK posted 2 pics of herself and Bobby in a full embrace -- she even says, "I got a running start" to jump into his arms for the hug.

Bobbi Kristina was grinning from ear-to-ear and added ... "My face says it all. I love you daddy."

Pretty amazing ... they've been estranged since Whitney Houston's death 2 1/2 years ago.

Still unclear why or how they buried the hatchet, but they've come a looooong way. Just 3 months ago ... we talked to Bobby and he acted like he didn't know BK had gotten married to Nick Gordon.