Theoretical investigations of the hyperfine quenching of the two metastable levels 1s22s22p63s3p 3P0 and 3P2 have been performed along the magnesium-like iso-electronic sequence ranging from Z = 12 to Z = 31. It is shown that the lifetime of the latter level is sensitive to hyperfine quenching in the beginning of the sequence, but that this sensitivity decreases going to higher Z. It is also shown that the branching fractions of the 3s2 1S0-3s3p 3P2 and 3s3p 3P1-3s3p 3P2 transitions are very sensitive to hyperfine quenching, which could lead to some dramatic effects in the spectrum. Our predicted transition rates of the hyperfine induced 3s2 1S0-3s3p 3P0 transition are compared to earlier results and some disagreements are found and explained. The present predicted lifetime of 3s3p 3P0 in 27Al+ is slightly longer than the recent measurement, but in better agreement than earlier predictions.