Emojis on my bio?

MomOf2 โ€ข Married ๐Ÿ’ DD:4yrs old ๐Ÿ‘‘ Angel Baby 5/6/2014 ๐Ÿ‘ผ My Rainbow Baby! 5/21/2015 ๐Ÿ‘ถ๐Ÿผ๐Ÿ’™
I was just wondering why do the emojis turn into '?' after I apply them to my bio? Can they still be viewed or are emojis not allowed on bio? 
โ€‹Thanks!