Yes, it is possible to book lower berth quota tickets online via IRCTC website. Here's the procedure -
Login to your IRCTC account and use the 'Plan My Journey' or 'Quick Book' section to search for train/berth availability. After selecting the desired class (AC 3-Tier, Sleeper etc), click on the 'Book' button. As usual, fill in the passenger details and make sure to select 'Lower' from the drop-down menu under the 5th column - 'Berth Preference'. Also ensure that you are ticking the respective check-boxes under 'Senior Citizen' column (6th column).
Now scroll down to the bottom of the page (on the same screen) and you will see a number of check boxes and radio buttons. If you wish to book lower berth quota tickets for both of your parents, then you should select the radio button next to '
Book, only if 2 lower berths are allotted'. If only a single lower berth is sufficient, then you may select the option '
Book, only if at least 1 lower berth is allotted'.
Here's a screenshot highlighting the lower berth ticket booking options -
Then click on the 'Next' button to go to the payment processing page.
That's all you need to do to book lower berth train tickets online. If lower berths are available, the system will process your booking, otherwise no tickets will be booked and a booking failure notification will be displayed to you.
Regards,
Deb