Perform for your family. You've given yourself your best shot at finding out whether you can sing: you picked a song within your range, learned out to sing it using the right technique, and practiced until you had it memorized.
When your performance is finished, ask your family to give you an honest opinion. No matter what they say, you should probably take it with a grain of salt; they may try to save your feelings or give you a good ribbing, as families sometimes do. However, their reaction should give you an inkling about whether your voice is good. If you feel confident enough to keep going, it's time to take it to the next level.
Perform in public. There are many opportunities to perform in public: you can go to an open microphone night at a club or lounge, sign up for a talent show, or do karaoke. Find a venue that works for you and prepare to sing a song for strangers.
As you sing, watch the crowd's reaction. They aren't as invested as your family in making sure you walk away with your self-esteem intact, so you may be able to get a better sense of whether your voice is easy on the ears.
Have a friend in the crowd ask some strangers whether they thought you were a good singer. Random strangers don't always appreciate being polled, so you shouldn't place your singing future in their hands
I am a professional singer