Hi @supritha,
Thank you for your question and welcome to the Bunnings Workshop community, it is great to have you with us.
I suspect the reason that the grout around your tile edges is cracking is due to slight movement and the inelastic nature of grout. It is unlikely that the steps are tied into the structure of the brick so when the brick or the steps move, which will always happen over time, the grout will crack.
Typically, in this application grout should not be used for these joins as it is inelastic and will not flex with the movement of the two separate masses.
My suggestion would be to remove any of the cracking grout using a grout saw and a wire brush. Once removed, the grout should be replaced with Sika 11FC in a suitable colour.
Have a look at How To Silicone a Gap for some guidance on how to carry out this job.
Let me know if you require further assistance.
Jacob
