My husband's family is a family that sings... a lot. They take tunes that they know and change the words to fit the situation. It can really be quite funny - either the lyrics themselves... or just how bad the song gets butchered. It's one of those that are you are either laughing with them or at them, but either way, we are laughing.
My son just recently started singing songs and remembering them. It has been a slow progression since he was about 2 1/2 years old, but I noticed the other day that he really does know most of the lyrics of songs now! Of course, he's singing: Twinkle Twinkle Little Star, Jesus Loves Me, Baby Beluga, Row Row Row Your Boat, etc. These are not top 10 hits (except for in our mini-van). One of his favorite songs in the Spiderman theme song (the original, from the 1960s). That one always cracks me up.
It made me start to think about when kids started to sing. Of course, every child is different. However, kids should usually start to sing songs and follow along with a tune between ages 2 and 3. That doesn't mean that you start introducing music at age 2. Kids need to have music around them from the time they are infants. When I saw music, I mean lullabies, praise and worship songs (if you are religious), kids songs with catchy beats, instrumental music, etc. There are so many benefits - learning to tap out of beat (first you will tap it out on their leg or bounce them as they listen), rhyming, variation in pitch, etc. You may not be a world class singer, but your child doesn't mind and he/she needs to hear your voice. Sing to your child/children when you put them to bed, wake them up, in the car, etc. Music development