As far as Alexander's first appearance goes, when K'Ehleyr first appeared, it seemed Worf had already had a previous relationship with her, so, I assumed she already had Alexander from that previous relationship, and just didn't bother telling Worf about him? So, I never questioned him being about6 on his first appearance.
But, yea, Teenager Alexander was definitely a case of Soap Opera Rapid Aging Syndrome (SORAS)
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